He later appears, equally sleepy, at the Knave of Hearts' trial and voices resentment at Alice for growing, and his last interaction with any character is his being "suppressed" (amongst other things) by the Queen for shouting out that tarts are made of treacle.
He panics at the mention of the word "cat", much like The Mouse from the book, and needs to have jam spread on his nose in order to calm down.
This first happens when Alice talks about her cat Dinah, causing the March Hare and the Mad Hatter to chase after it in order to administer the jam.
She also appears in the movie's 2016 sequel in the beginning when Alice returns to Wonderland, and later when Time travels back to the past and encounters her, the Hatter and the March Hare having a tea party, which he curses to last forever after he realizes they are stalling him.
The cadence of this enigmatic lyric has inspired references over the next century, including the title of John Markoff's 2005 book, What the Dormouse Said: How the 60s Counterculture Shaped the Personal Computer Industry.